The present invention relates to a transmission power output shaft assembly, and more particularly relates to a transmission power output shaft assembly which provides good and assured lubrication for a bearing which supports the end of a transmission power output shaft proximate to a power output gear wheel thereof.
Nowadays the front engine front wheel drive type of automotive vehicle configuration, or the so called FF configuration, is becoming more and more popular. Further, automatic transmissions for such front engine front wheel drive automotive vehicles are undergoing much development. One form of such an automatic transmission for a front engine front wheel drive automotive vehicle which has been conceived of, and constructed, incorporates a fluid torque converter and a gear transmission mechanism arranged in line, and a power output shaft arranged under this in line assembly of the fluid torque converter and the gear transmission mechanism to extend in parallel to the general axis of said assembly, with its end remote from the fluid torque converter rotationally driven by a power output member of the gear transmission mechanism, and with its other end close to the fluid torque converter being provided with a power output gear which is meshed with a power input gear wheel of a differential mechanism. This constructional arrangement is widely accepted because of its compactness and convenience, especially in the case of a transversely mounted engine/transmission assembly; and it is very helpful from the point of view of minimizing the axial length of the vehicle transmission as a whole.
In such a construction, the power output shaft must of course be supported from the casing of the transmission via bearings such as roller bearings or the like. Now, the power output shaft support bearing on the end of the power output shaft to which is fitted the power output gear wheel is typically fitted just inboard of said power output gear wheel, i.e. on the side of said power output gear wheel remote from the end of the power output shaft. Thus, this support bearing comes to be sandwiched between the power output gear wheel and (typically) a bearing holder which is mounted to the transmission casing and holds the support bearing. In this connection, the question arises as to how proper lubrication is to be provided for this support bearing. Because typically the power output gear wheel mounted as explained above on the end of the power output shaft closer to the fluid torque converter is closely surrounded, by a part of the transmission casing, good access to the aforesaid support bearing mounted just inboard of this power output gear wheel is not available past this power output gear wheel, and accordingly splash lubrication from within the part of the transmission casing that encloses the transmission power output gear wheel and the differential power input gear meshed therewith cannot be relied upon the lubricating this support bearing, in view of such limited access available thereto.
Accordingly, it might be conceived of to provide a lubricant passage within the power output shaft, with one end thereof opening at its end at which the power output gear wheel is fitted, and with the other end thereof opening in the vicinity of the support bearing. Thus lubricant from within the part of the transmission casing that encloses the transmission power output gear wheel and the differential power input gear meshed therewith which is splashed around by said differential power input gear so as to impinge upon said end of the power output shaft would be able to enter into this lubricant passage so as to pass therethrough to be supplied to the support bearing. Therefore passage of lubricant past the power output gear wheel, between its outer peripheral surface and the inner confronting surface of the transmission casing, would not be relied upon for supply of lubricant to the support bearing.
This form of construction would provide better lubrication for the support bearing than a construction incorporating no lubrication passage at all. However, the difficulty would arise with this form of construction that the lubricant provided within the part of the transmission casing that encloses the transmission power output gear wheel and the differential power input gear meshed therewith, which lies as a matter of course at the bottom portion of said part of said transmission casing, and which is thus splashed around by said differential power input gear (by a lower part of the periphery of said differential power input gear passing through said lubricant and by adhering of said lubricant thereon for a time) so as to impinge upon said end of the power output shaft, is necessarily moving at quite a high speed, particularly when the vehicle incorporating this transmission is being operated in the high road speed operational region. Accordingly, particularly in this high vehicle road speed operational region, it would be difficult for this splashed around lubricant to enter into the lubricant passage in the power output shaft, owing to the velocity of this lubricant, and thus the problem of adequate lubrication of the support bearing of the power output shaft would not be adequately resolved.